Patent Document 1 discloses a projector that is provided with a lighting device that employs a phosphor as a light source.
The lighting device includes a first blue semiconductor laser, a second blue semiconductor laser, a dichroic mirror, a phosphor wheel, a wavelength selection wheel, and a rod integrator. The first blue semiconductor laser supplies first blue light (excitation light) having a wavelength of approximately 450 nm. The second blue semiconductor laser supplies second blue light (illumination light) having a wavelength of approximately 460 nm.
The first blue light supplied from the first blue semiconductor laser is incident to one surface of the dichroic mirror at an angle of incidence of approximately 450. The dichroic mirror is a color combination element in which the cutoff wavelength is set to approximately 90 nm and has characteristics of high reflectivity for a wavelength component which is shorter than the cutoff wavelength and high transmission for a wavelength component which is longer than the cutoff wavelength. The first blue light is reflected by one surface of the dichroic mirror.
The first blue light that is reflected by the dichroic mirror is incident to the phosphor wheel by way of a lens group. The phosphor wheel has a phosphor region that contains a phosphor that emits yellow fluorescent light in response to excitation by the first blue light. The yellow fluorescent light (illumination light) from the phosphor region is incident to the dichroic mirror by way of a lens group. The yellow fluorescent light is transmitted through the dichroic mirror.
The second blue light that is supplied from the first blue semiconductor laser is incident to the other surface of the dichroic mirror at an angle of incidence of approximately 45°. The second blue light is reflected by this other surface of the dichroic mirror.
The yellow fluorescent light that is transmitted through the dichroic mirror and the second blue light that is reflected by the other surface of the dichroic mirror are incident to one end surface of the rod integrator along the same light path. The yellow fluorescent light and second blue light that are emitted from the other end surface of the rod integrator are incident to the wavelength-selection wheel. The wavelength-selection wheel has first to third wavelength-selection regions.
The first wavelength-selection region has a high transmission characteristic for the blue component and red component and a high reflection characteristic for the green component, the cutoff wavelengths being 490 nm and 600 nm, respectively. The second wavelength-selection region has a high transmission characteristic for the blue component and the green component and a high reflection characteristic for the red component, the cutoff wavelength being 600 nm. The third wavelength-selection region has a high transmission characteristic across the entire range of visible wavelengths.
The light that is emitted from the rod integrator is successively irradiated into the first to third wavelength-selection regions. By controlling the lighting operation of the first blue light source and second blue light source in synchronization with the rotation operation of the wavelength-selection wheel, red light, green light, blue light, and white light are successively emitted from the wavelength-selection wheel. The red light, green light, blue light, and white light that are emitted from the wavelength-selection wheel are the output light of the lighting device.
The output light of the lighting device is irradiated into a digital micromirror device (DMD). The DMD successively forms images of each of the colors red, green, and blue. The images of each of the colors formed by the DMD are enlarged and projected upon a screen by way of a projection lens.